Conveyor transfer apparatus pickup and dropoff sensor

ABSTRACT

A method of transferring an article carried by a first moving conveyor to a second moving conveyor and apparatus for effecting the same. The transfer is effected by a pickup device lifting the article from the first conveyor, transporting it to adjacent the second conveyor, and permitting the second conveyor to receive the transported article for further conveying thereof by the second conveyor. The article may be suspended from a hanger removably supported on a hook of the first conveyor. A sensor is provided for sensing proximity of the hanger to the pickup device for controlling initiation of the raising of the hanger from the hook to pick up the article and free it from the hook for delivery of the lifted article to the second conveyor. Upon delivery of the article to the second conveyor, the transfer is sensed by the proximity sensor when the hanger is removed from the pickup device and in response thereto, the transferring apparatus is returned to a start position for effecting transfer of a subsequent article from the first conveyor to the second conveyor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to material handling methods and apparatus and inparticular to a method of transferring an article from a first movingconveyor to a second moving conveyor and apparatus for effecting thesame.

2. Description of the Prior Art

In one conventional form of conveyor such as used in assembly lines inthe manufacture of appliances, such as washers and the like, relativelybulky and heavy articles, such as washer cabinets and the like, areconveyed by conveyors along preselected assembly lines. The article mayconventionally be suspended from hooks on the conveyors by means ofsuitable hangers associated with the articles.

In many applications, the articles must be subsequently transferred to asecond conveyor for further manufacturing operations on a subsequentassembly line or for delivery of the articles such as for warehousingand the like. It has been conventional to manually remove the articlesfrom the first conveyor and transfer the articles to the secondconveyor. Such manual transferring operation is costly, and physicallydifficult for workers especially when the articles are relatively heavyand unwieldy. Commercially available parts transfer apparatus such asindustrial robots are not capable of exercising the human judgementnecessary to transfer articles to a conveyor on which it is necessary toadd articles selectively.

Even industrial robots which are programable, such as those availablefrom Auto Place, Inc. of Troy, Michigan, are not capable of operatingunder many conditions existing in modern industrial facilities.

Prior art apparatus such as shown in U.S. Pat. Nos. 2,628,702;2,771,174; and 3,370,723 do not meet the needs of an application whereselective transfer of articles is desirable or required.

SUMMARY OF THE INVENTION

The present invention comprehends an improved method of transferringarticles carried by a first moving conveyor to a second moving conveyor,and apparatus for effecting the same which effectively eliminates thedisadvantages of the prior art transferring methods and apparatus in anovel and simple manner. The invention comprehends the method ofeffecting such a transfer wherein a transferring device is mountedbetween the first and second conveyors and includes improved means forsensing the presentation of an article to be transferred at a pickupposition. The transferring device effects a pickup of the article,transports the picked-up article to a dropoff position at the secondconveyor, effects transfer of the article to the second conveyor andreturns to a start position for effecting a subsequent similar articletransfer.

In the illustrated embodiment, the transfer means is arranged to liftthe article from the first conveyor where the article is suspended fromhooks on the first conveyor by means of an associated hanger. Theapparatus illustratively comprises a carrier which is mounted forswinging about a pivot axis and which carries at its distal end a pickupdevice, or hand, which is adapted to engage the hanger of the article,lift it from the hook on which it is suspended, and swing the liftedarticle to the dropoff position adjacent the second conveyor.

The transferring apparatus is positioned at the start position upstreamof the pickup position so that the pickup device effectively pursues thearticle to be transferred on the first conveyor. When the pickup deviceengages the hanger, the engagement is sensed and the lifting of thearticle is effected automatically as an incident of such sensing. At thesame time, the pickup device may be locked to the hanger to preventinadvertent dropping of the article during the transfer operation.

More specifically, the invention comprehends the provision of a sensorfor determining the presence of the suspended article on the firstconveyor upstream of the pickup position. A proximity sensor may beprovided on the pickup device for sensing the catching of the hanger bythe pickup device in the pickup operation. The apparatus may includemeans for effecting a temporary discontinuation of the swing of thetransfer means during the lifting of the article from the first conveyorhook.

The removal of the transferred article from the pickup device to thesecond conveyor is also sensed in the present invention. In theillustrated embodiment, the transfer of the hanger from the pickupdevice to the second conveyor hook is sensed by the same proximitysensor that senses the juxtaposition of the hanger to the pickup deviceat the pickup position for initiating the lifting operation. The controlfurther includes means responsive to the sensing of the transfer of thehanger from the pickup device at the dropoff position to initiate returnof the carrier to a start position adjacent the pickup position forpicking up a subsequent article from the first conveyor in a mannersimilar to that above described.

Thus, the invention provides an improved facilitated, safe, low costtransfer of articles which conventionally are difficult to transfer asbetween conventional conveyors. The improved sensor apparatus isextremely simple and economical while yet providing the highly desirableadvantages discussed above.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the invention will be apparent from thefollowing description taken in connection with the accompanying drawingwherein:

FIG. 1 is a schematic plan view of a conveyor system and articletransferring apparatus embodying the invention;

FIG. 2 is a fragmentary front elevation of the transferring apparatus;

FIG. 2a is a fragmentary perspective view of the pickup device of thetransfer apparatus;

FIG. 3 is a fragmentary enlarged left side elevation of the transferringapparatus;

FIG. 4 is a fragmentary rear elevation of the transferring apparatus;

FIG. 5 is a fragmentary elevation of the conveyor system at the dropoffposition;

FIG. 6 is a fragmentary vertical section taken substantially along theline 6--6 of FIG. 5;

FIG. 7 is a fragmentary elevation of the conveyor system at the pickupposition;

FIG. 8 is a fragmentary vertical section taken substantially along theline 8--8 of FIG. 7;

FIG. 9 is a pneumatic flow diagram of the transfer apparatus control;and

FIG. 10 is a schematic wiring diagram of the electrical components ofthe control.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the exemplary embodiment of the invention as disclosed in thedrawing, a transfer apparatus generally designated 10 is provided fortransferring an article, such as a washer cabinet or the like, from afirst moving conveyor generally designated 11 to a second movingconveyor generally designated 12.

Conveyor 11, as shown in FIG. 7, may comprise a conventional chain andhook conveyor provided with a plurality of hooks 13 carried on suitablerollers 14 rolling on support channels 15 and moved therealong by asuitable driven chain 16. As shown in FIGS. 5 and 6, conveyor 12similarly comprises a conventional chain and hook conveyor includinghooks 17 carried on rollers 18 supported on support channels 19 movedtherealong by a driven chain 20.

As shown in FIG. 1, conveyors 11 and 12 may comprise spaced,side-by-side conveyors, such as conventionally employed in assembly linemanufacturing operations. Transfer apparatus 10 may be mountedintermediate conveyors 11 and 12 for picking up the articles at a pickupstation or position generally designated 21 and for dropping off thetransferred articles at a dropoff station or position generallydesignated 22. In the illustrated embodiment, apparatus 10 comprises acommercially available industrial robot modified in accordance with theinvention. It is available from Auto Place, Inc. of Troy, Michigan andincludes a carrier generally designated 23 mounted on a support 24 forrotation about a pivot axis 25. A pickup device generally designated 26is provided on an arm 27 of carrier 23 for engaging the article to betransferred, supporting it during the transfer operation, and droppingit off to the second conveyor in a dropoff operation.

The support 24 includes a base 28 carrying a lift cylinder 29, and areach and retract cylinder 31. Such transferring apparatus isconventionally operated by suitable fluid operated means for effectingmovement of the arm 27 and pickup device 26 about the axis 25 ineffecting the desired article transfer. In the illustrated embodiment,the operation of apparatus 10 is controlled by solenoid operated,pneumatic valves as schematically illustrated in FIGS. 10 and 11, itbeing understood that other suitable controls may be utilized within thescope of the invention.

As shown in FIG. 2a, the pickup device, or hand, 26 includes a mountingblock 32 provided with fingers 33 and 34 and a backup plate 35. A clampcylinder 36 is mounted to the block 32 by suitable supports 37 and isprovided with a clamp piston 38 which is selectively movable toward andaway from backup plate 35 for cooperating with fingers 33 and 34 inlocking a hanger 39 selectively in the pickup device.

More specifically, the fingers are spaced apart to define a hangerreceiving space 40. At their inner ends, each of the fingers defines anupwardly facing support surface 41 extending from a vertical stopsurface 42 on block 32. The hanger includes a crosspiece 43 spaced belowan upper hook portion 44 which is adapted to rest on surfaces 41 inabutment with stop surface 42 in the picked-up arrangement illustratedin FIG. 2a. Bracket 35 defines a notch 45 in which a lower portion 46 ofthe hanger is received and clamped by the piston 38 in the picked-uparrangement to effectively lock the hanger to the pickup device duringthe transfer of the article from conveyor 11 to conveyor 12.

A proximity detector 47 is mounted on block 32 adjacent stop surface 42for sensing the reception of the hanger 39 in the pickup device. Thedetector may comprise a conventional proximity sensing means includingsuitable switch contacts for use in electrically controlling certainphases of the transfer operation, as will be brought out more fullyhereinafter.

As further shown in FIG 2a, a contact 48 upstands from the block 32.Contact 48 is adapted to cooperate with a pair of plates 49 and 50defining a cam rail generally designated 51 at the pickup position 21,as illustrated in FIG. 1. As will be brought out more fully hereinafter,the cooperation of contact 48 and cam rail 51 causes the pickup deviceto move parallel to the substantially rectilinear path of movement ofthe conveyor 11 at the pickup position 21 notwithstanding the normalarcuate on cylinder 31.

Referring now more specifically to FIGS. 2-4, cylinder 31 is providedwith pressurized air supply connections 52 and 53 for variably extendingand retracting respectively the arm 27 relative to the axis 25. Arm 27comprises the piston of cylinder 31 to define a selectively extensiblecarrier 23 for selectively spacing the pickup device 26 relative to thepivot axis 25.

Carrier 23, and more specifically cylinder 31, is supported on the upperend of a piston 54 of the lift cylinder 29 which is selectivelyvertically adjusted by means of pressurized air delivered to thecylinder through a lift hose connection 55 and a drop hose connection56.

Rotation of carrier 23 about axis 25 is effected by a piston 57 movablein rotate cylinder 30 as a result of pressurized air delivered theretothrough a first hose connection 58 and a second hose connection 59.Piston 57 is mechanically linked to a rack 60 by means of a plate 61.The rack meshes with a pinion gear not shown on the piston 54 forrotating the piston and thus rotating the carrier 23 as a function ofthe pressurized air delivered through the hose connections 58 and 59. Inthe illustrated embodiment, air delivered through hose connection 58rotates the carrier in a clockwise direction, as seen in FIG. 1, the airdelivered through hose connection 59 rotates the carrier in acounterclockwise direction as seen therein.

As indicated briefly above, it is desirable to cushion the stopping ofthe transfer operation. To effect such cushioning, a cushioning cylinder63 is mounted on a plate 64 carried on the base 28. Cylinder 63 isprovided with a plunger 65 extending freely through an aperture 66 inplate 61 and provided at its distal end with an adjustably threaded nut67 which is adapted to engage a stop 68 during clockwise rotation of thecarrier 23.

A pair of switches 69 and 70 are provided on base 28 for controllingoperation of the rotate cylinder 30 and a stop cylinder 71 (FIG. 4),respectively. Pressurized air is delivered to the stop cylinder througha "stop" hose connection 72 and a "pass" hose connection 73. Stop 68 isprovided on the piston 74 of the cylinder 71. As shown in FIG. 4,cylinder 71 is mounted to plate 61 for movement therewith relative tothe nut 67 on plunger 65.

Referring now to FIG. 7, the cam rail 51 is mounted on an angle iron andmetal plate support 75 which also carries a switch 76. As shown in FIGS.7 and 8, a pair of brushes 77 and 78 are mounted to the support 75 forwiping engagement with the hooks 17 at the pickup position 21 to swingthe hooks reversely, as shown in FIG. 7, as the article is being liftedfrom the hook at the pickup position or station 21. Other means offrictionally engaging the hooks to cause them to swing reversely couldalso be employed.

Referring now to FIGS. 5 and 6, a plurality of sensor switches 79, 80,81 and 82 are provided on a plurality of mounting brackets 83, 84 and 85carried by the support channels 19 at spaced positions adjacent thedropoff position 22. Switches 79, 80, and 82 are provided for sensingthe capability of conveyor 12 to receive the article to be transferredand more specifically sense the presence or absence of a hanger on therespective hooks 17. Switch 81 comprises a detection switch fordetecting when a hanger has been taken from the pickup device of thetransfer apparatus 10 by a hook, indicating the desired transfer toconveyor 12. As shown in FIGS. 1 and 5, switches 79, 80, 81 and 82 areprovided with "cat whisker" probes 86.

In the illustrated embodiment, operation of apparatus 10 is effected bya pneumatic system generally designated 87 diagrammatically illustratedin FIG. 9. Air is delivered from a supply of pressurized air to thesystem through a master control generally designated 88. The systemincludes a plurality of solenoid valves, including a high-low valve 89,a retract valve 90, a reach valve 91, a rotate valve 92, a stop valve93, an up valve 94, a start valve 95, and a dropoff valve 96.

High-low valve 89 comprises a three-way valve having a normally closedport 89a, a normally open port 89b, and an inlet port 89c. Port 89b isconnected to hose connection 58. The valve is controlled by a solenoid103 (FIG. 10). Port 89a communicates with hose connection 58 through aflow control valve 97 for providing a low pressure operation of therotate cylinder through hose connection 58.

Retract valve 90 is controlled by a pair of solenoids to comprise amaintained position valve having an inlet port 90a, an exhaust port 90b,and an outlet port 90c connected to hose connection 53. The retractvalve is operated by solenoids 98 and 99 (FIG. 10). Solenoid 99 closesthe valve to cause the exhaust port 90b to communicate with the outletport 90c. Energization of solenoid 98 causes opening of the valve inwhich the inlet port 90a communicates with the outlet port 90c. Theinlet port 90a is connected to the control 88 through a line 100 and theexhaust port 90b is connected to the reach valve 91 through a line 101.

The reach valve 91, controlled by solenoid 104 (FIG. 10), is a doublevalve having a normally closed port 91a connected by line 101 to port90b of the retract valve 90. The reach valve further includes a normallyopen port 91b and an inlet port 91c connected to the control 88 by aline 102. Port 91b is connected to connection 52 of the reach andretract cylinder 31 for causing extension of the arm 27 relative tocylinder 31.

The rotate out valve 92 is controlled by a solenoid 105 (FIG. 10) andcomprises a normally open valve having an inlet port 92a connected tothe control 88, and an outlet port 92b connected to a flow control valve106. The flow control valve, in turn, is connected to the port 89c ofvalve 89.

Stop valve 93 is controlled by a solenoid 107 (FIG. 10) and comprises adouble valve having a normally closed port 93a which is connected toconnection 72 of stop cylinder 71, a normally open port 93b connected tohose connection 73 of the stop cylinder, and an inlet port 93c connectedto the control 88.

Up valve 94 is controlled by a solenoid 108 (FIG. 10) and comprises anormally closed valve having an inlet port 94a connected to the control88 and an outlet port 94b connected to hose connection 55 of liftcylinder 29 and cylinder 36 on the pickup device 26.

Start valve 95 is controlled by a solenoid 109 (FIG. 10) and comprises anormally closed valve having an inlet port 95a connected to the control88 and an outlet port 95b connected to the control 88.

The dropoff valve 96 is controlled by a solenoid 110 (FIG. 10) andcomprises a normally closed valve with an inlet port 96a connected tocontrol 88 and an outlet port 96b connected to the control 88.

Hose connection 59 of the rotate cylinder 30 is connected to the control88 by a line 111 and hose connection 56 is connected to the control 88by a line 112.

Control 88 comprises a programmable pneumatic control commerciallyavailable as a part of an apparatus identified as the "Auto Place Series50" parts transfer unit available from Auto Place, Inc., Troy, Michigan.

The control 88 comprises a bank of pneumatic valves which when actuatedcause the pneumatically operated apparatus to perform a sequence ofoperations in accordance with a pre-established program. For theapplication of the Auto Place apparatus to the invention the control wasprogrammed to cause the apparatus to perform, in sequence, the followingoperations:

start

lift and rotate (cw in FIG. 1)

drop

retract

rotate (ccw in FIG. 1)

time delay

reach

stop

Additional solenoid operated valves as described above were added tomodify the operation of the apparatus to achieve the desired results.

The specific mechanical detail of control 88 forms no part of thepresent invention except to the extent that it is programmed to provideair at specific times to appropriate air lines for accomplishing themethod of the invention and only those portions of the control necessaryto understand the operation of the transfer apparatus of the inventionare disclosed.

In describing the operation of the transfer apparatus, it will beassumed that the control elements illustrated in FIG. 11 are with theswitches in their normal position. In the start condition illustrated inFIG. 1 of the drawing, the transfer arm 27 is in the extended positionon cylinder 31 with the cylinder being in a lowered position of the liftcylinder means 29. As shown in FIGS. 1, 7 and 8 the first conveyor 11carries a switch 76 upstream of the pickup position 21. When a hook 13of the conveyor passes the switch 113 carrying an article on a hanger39, the hanger trips switch 76 to complete a circuit through a normallyclosed toggle switch 114 (FIG. 10) to the solenoid 109. As shown in FIG.10, the electrical portion of the system is connected to power supplyleads L1 and L2 and includes an input transformer 115 for dropping thepower supply voltage, which conventionally may be 120 volts, to a lowercontrol voltage, such as 24 volts. Operation of the circuit may be bydirect current and, thus, a full wave rectifier 116 may be connectedacross the secondary 115a of the transformer to provide full wave directcurrent to control leads 117 and 118, respectively. A filter condenser119 may be connected across the rectifier and lead 117 may be connectedto ground. The series connection of switches 76 and 114 and solenoid 109may be between leads 117 and 118, as shown in FIG. 11.

Energization of solenoid 109 opens start valve 95 (FIG. 9) to provide aburst of air to the control 88, which conditions the control to provideair to inlet port 94a of up valve 94 and to hose connection 58 of rotatecylinder 30 in accordance with program of the control. Valve 94,however, is closed at this time to prevent lifting of the arm 27.

Solenoids 103 and 105 are de-energized at this time so that valves 89and 92 permit the delivery of the high pressure air from control 88 tothe hose connection 58, thereby initiating rotation of the arm 27 aboutaxis 25. Since the delivery of air to the hose connection 58 is throughthe high flow connection of valve 89, the arm is rotated at maximumspeed so as to pursue and catch the hanger with the pickup device 26. Asbest shown in FIG. 1, the movement of the pickup device in a clockwisedirection causes contact 48 on the pickup device to enter a channelformed by plates 49 and 50 and to contact the plate 49, which iselectrically connected to the solenoid 104. As shown in FIG. 10, contact48 is connected to control lead 117 and, thus, a circuit is completed toenergize solenoid 104 of reach valve 91. Energization of the reach valvesolenoid closes normally open port 91b and opens normally closed port91a to supply air to port 90b of retract valve 90. The pressure of theair delivered to the valve 90 through port 90b overcomes the solenoid 98which is energized through the normally closed contact 47a of proximitydetector 47 and mechanically shifts the valve to the closed position inwhich air may pass from outlet port 90c to hose connection 53, therebycausing the retraction of arm 27.

The retraction of arm 27, however, substantially immediately causescontact 48 to become spaced from plate 49, thereby de-energizingsolenoid 104 to shift reach valve 91 back to its normal position whereair is supplied to hose connection 52 through the normally open port 91bof valve 91. This causes arm 27 to again move toward plate 49. Sincethere is a time lag in the operation of the valves, the arm could move asubstantial distance back from plate 49 during the time lag, however,this is prevented by plate 50 which engages contact 48 during retractionof arm 27. The rather rapid back and forth movement of the arm 27results in a sequence of incremental movements wherein the arm 27 iscaused to reach and retract incrementally to cause the pickup device 26to follow the channel between plates 49 and 50 as the arm 27 is rotatedin a clockwise direction, as seen in FIG. 1. Since the arcuate channelis constructed with a radius of curvature which compensates for theradius of curvature of the path of movement of contact 48, the pickupdevice follows a substantially rectilinear path parallel to the path ofmovement of the conveyor 11 at pickup position 21. The back and forthincremental movement of the pickup device 26 has a beneficial effect infinding and seating the hangers in the fingers 33 and 34 of the pickupdevice. In some applications a smoother pickup movement might bedesirable in which case the conveyor track could be constructed with anarcuate section paralleling the path of the pickup device in which casethe plates 49 and 50 could be eliminated. In other applications agreater tolerance for hunting might be acceptable in which case theplate 50 might be eliminated, thus allowing the switching of the valvesto provide all of the compensation for the arcuate movement of thepickup device.

As indicated above, the rotation of carrier 23 is caused to be at highspeed so as to cause the pickup device to pursue and catch the hanger39, carrying the article to be transferred, at the pickup position 21.When the pickup device catches the hanger, as shown in FIG. 2a, theproximity switch 47 is actuated so as to open contacts 47a, thusde-energizing solenoid 98. At the same time, normally open contacts 47band 47c of proximity switch 47 are closed, thereby energizing solenoids99, 108, 103, and 105. De-energization of solenoid 98 and energizationof solenoid 99 closes retract valve 90 so that inlet port 90b is incommunication with outlet port 90c to permit continuation of thereach-retract incremental action until the pickup device is swung pastthe right-hand end of the plate 49, as shown in FIG. 1.

Energization of solenoid 105 causes air to be removed from the rotatecylinder momentarily for a purpose hereinafter explained.

The concurrent energization of solenoid 108 causes the up valve 94 toopen, thus supplying air to clamp cylinder 36 and hose connection 55,thereby clamping the hanger in the pickup device and concurrentlylifting the hanger from the hook 13.

As shown in FIGS. 7 and 8, the lifting of hanger 39 from the hook 13permits brushes 77 and 78 to pivot the hook in a clockwise directionabout a pivot point 9, as shown in FIG. 7, as a result of the frictionalengagement of the brushes with the hook as the hook is carried past thepickup position by chain 16.

The pivoting of the hooks 13 is desirable because it provides a morepositive and quicker release of the hangers 39 from the hooks. Also asthe pickup device nears the end of the pickup station it is desirable tobegin to slow its speed as hereinafter described. If for any reason thepickup device has not successfully picked up a loaded hanger untilnearing the end of the pickup station, the combination of the speed ofthe conveyor and the reducing speed of the pickup device could cause ahanger to hang up on a hook. The brushes 77 and 78 effectively preventsuch a hang up by causing the hook to be pivoted upwardly out ofengagement position with the hanger 39.

When transfer of the support of the article is effected to the pickupdevice 26 and support arm 27, the high speed rotation of the arm may bediscontinued so as to reduce initial forces on the article beingtransferred. This is automatically effected by the energization ofsolenoid 103 at this time to open port 89a of high-low valve 89 andclose port 89b thereof permitting the air supply to hose connection 58to now be effected through the flow control valve 97 which effectivelyreduces the air pressure and concurrently reduces the rotational speedof carrier 23.

Referring now to FIGS. 2 and 10, a switch 120 is carried on a bracket121 attached to the reach and retract cylinder 31 to have selectiveengagement with a stop 122 carried on the top of lift cylinder 29 whenthe carrier 23 is raised to an upper position. Switch 120 comprises anormally closed switch connected in series with a second set of normallyopen contacts 47c of proximity switch 47 to complete a circuit tosolenoids 105 and 107 under the condition that the proximity switch hassensed the presence of the hanger 39 in the pickup device 26 but has notraised the pickup device and hanger as yet to the lifted position. Thisfunctioning permits the lifting of the article to be effected withoutconcurrent forceful rotation of the carrier as the energization ofsolenoid 105 closes valve 92 to interrupt air flow to the valve 89 and,thus, to the rotate cylinder hose connection 58. Upon opening of switch120 at the upper limit of movement of the lift cylinder piston 54,solenoids 105 and 107 are de-energized, permitting valve 92 to open andthereby restore normal operation of the high-low valve 89 wherein therotate cylinder is operated to rotate the arm in a clockwise direction,as seen in FIG. 1, to bring the article toward second conveyor 12.

In assembly line operations, it is possible for the second conveyor, attimes, to be not in a condition for receiving the article to betransferred from the first conveyor. Illustratively, at the time thearticle being transferred is being swung on the carrier 23 towardconveyor 12, the next hook, or hooks, on conveyor 12 may be alreadycarrying a suspended article so that they are not available forreceiving the article being transferred. It is, therefore, necessary tointerrupt the transfer operation until such time as an available hook isbrought to the dropoff position 22 to accept the article beingtransferred. The determination of the capability of the second conveyorto receive the article is effected by switches 79, 80 and 82. Switch 79comprises a normally open switch which, when closed, completes a circuitto a holding relay coil 123. The holding relay further includes normallyopen contacts 123a band 123b which are closed by the energization ofrelay 123.

As shown in FIG. 10, switch 80 is connected in series with coil 123 and,thus, when the hook carrying the hanger 39 closes switch 79, the circuitis maintained to coil 123 until the hanger engages the probe 86 ofswitch 80. The second set of holding contacts 123b are connected inseries with the coil 124 of a second relay which is provided with afirst set of normally open holding contacts 124a and a second set ofnormally open holding contacts 124b. Energization of coil 124 closescontacts 124a to hold in the relay through a series circuit of contacts124a and a normally closed switch 82. Closing of contacts 124b completesa circuit to solenoid 107 through normally open switch 70 (FIG. 3).Switch 70 is closed as a result of the movement of piston 57 which movesplate 61 to the left, as seen in FIG. 3, to operate switch 70 atapproximately the time pickup device 26 moves past the right-hand end ofplate 49, as seen in FIG. 1.

Energization of solenoid 107 operates stop valve 93 to open the normallyclosed outlet port 93a to supply air to hose connection 72 of the stopcylinder 71, thus moving piston 74 to the right, as shown in FIG. 4, tobring stop 68 on piston 74 into interfering relationship with nut 67 onplunger 65 of cushioning cylinder 63.

Referring now to FIG. 3, as the plate 61 carried by the piston 57 ofrotate cylinder 30 is moved to the left, plate 61 comes into contactwith stop 68 on piston 74 prior to the time that plate 61 normally wouldhave contacted nut 67 had the piston 74 been in a retracted position.Thus, when the stop cylinder 71 is actuated, carrier 23 is stopped in aposition intermediate the two conveyors, as shown in broken lines inFIG. 1. The stopping is cushioned by the action of cushioning cylinder63 so as to prevent undesirable swinging of the suspended articlenotwithstanding the abrupt termination of the swinging movement at theintermediate position.

When the hanger 39 causes opening of normally closed switch 80 as thehanger is moved to the left, as seen in FIG. 1, the holding circuit torelay 123 is broken, thus opening the holding contacts 123a and 123b. Atthis time, however, relay 124 remains energized through the holdingcontacts 124a and the normally closed switch 82 on the conveyor 12.Carrier 23 remains positioned in the intermediate position by theabutment of stop 68 against nut 67.

In the event that the following hook on conveyor 12 does not carry ahanger, switch 79 is not reactuated as the hanger moves from switch 80to switch 82 in the normal movement of conveyor 12. The hanger opensswitch 82 to de-energize relay 124 which, in turn, opens its holdingcontacts 124a and 124b to further de-energize solenoid 107.

De-energization of solenoid 107 allows stop valve 93 to return to itsnormal condition wherein air is provided to "pass" hose connection 73causing the piston 74 of the stop cylinder 71 to be retracted andthereby freeing the rotate cylinder piston 57 for further movement untilplate 61 contacts the nut 67 to provide a final limitation on therotational movement of the carrier to drop off position 22 as shown indot-dash lines in FIG. 1.

It should be noted that if the second hook also contained a hanger,switch 79 would have been reclosed prior to the opening of switch 82,thus re-energizing the holding relay 123 and permitting its holdingcontacts 123a and 123b to be maintained closed, relay coil 123 beingenergized through the maintained closed switch 80. In this event, whenswitch 82 is opened by the first hanger, relay 124 would remainenergized through contact 123b of the first holding relay 123notwithstanding the opening of switch 82, thereby maintaining contacts124a closed to hold in relay 124 and maintaining contacts 124b closed tomaintain energization of solenoid 107, thereby maintaining the stoppageof the carrier at the intermediate position.

As the sensing operations of the switches 79, 80 and 82 must be effectedsequentially as discussed above, the spacing therebetween must be lessthan the minimum spacing between all pairs of hooks on the conveyor toassure the prevention of completion of the transfer operation to anon-empty hook. The location of the spaced switches relative to thedropoff position 22, however, is a function of the speed of the conveyor12 and the rotational speed of carrier 23 which must be correlated toassure that the carrier will bring the suspended article to the dropoffposition 22 suitably to have the suspended article picked up by the nextempty hook 17, as determined by the switches as discussed above.Normally closed switch 69, in series with solenoid 103, is opened by thepiston 57 slightly before the carrier reaches the dropoff position toagain cushion the stopping of the carrier for effectively avoidinginertia problems in the stopping operation. Thus, in the normaloperation of the transfer apparatus, the transfer may or may not bestopped at the intermediate position depending on the condition of thehooks on the second conveyor to receive the article being transferred.In the event that all hooks being brought to the dropoff position areempty, all transfer operations would be uninterrupted with the carrierbeing swung in a continuous movement from the pickup position to thedropoff position. The carrier, however, may be temporarily retained atthe start position awaiting the movement of an article to be transferredby the first carrier to the pickup position, as discussed above.

When the carrier is swung to the dropoff position, it positions thesuspended article suitably to permit the upcoming hook to engage portion44 of the hanger 39 to remove the hanger and article from the pickupdevice 26. Such removal is sensed by the proximity switch 47 and thuslyresults in the opening of contacts 47b and 47c and closing of contacts47a. Resultingly, solenoids 99, 108 and 103 are de-energized andsolenoid 98 is energized. De-energization of solenoid 108 closes the upvalve 94 causing back pressure to control 88 which causes the control tostep to its drop operation at the completion of which it steps to itsretract operation to supply air through the now open valve 90 which wasopened as a result of the de-energization of solenoid 99 andenergization of solenoid 98. De-energization of solenoid 103 permits thehigh-low valve to return to the normal position wherein the flowtherefrom is from the high pressure outlet port 89b.

The downward movement of the carrier causes actuation of switch 81 whichis connected in series with a relay coil 125 having a normally opencontact 125a connected in series with solenoid 110. The energization ofcoil 125 effects a closing of the contacts 125a which completes acircuit to the solenoid 110 of dropoff valve 96 to open the normallyclosed valve allowing a pulse of air to step the control 88 for shiftingair to the rotate in hose connection 59 of the rotate cylinder 30 forreturning the carrier to the start position. In the start position,control 88 steps to a short time delay and then on to reach and stopsteps.

Return of the carrier 23 to the start position is effected by thecontrol 88 for transferring subsequent articles from conveyor 11 toconveyor 12 in a similar manner as discussed above.

Having described the invention, the embodiments of the invention inwhich an exclusive property or privilege is claimed are defined asfollows:
 1. In an apparatus for transferring an article from a firstmoving conveyor to a second moving conveyor, said apparatus having acarrier provided with a pickup device, means for raising the carrier tocause the pickup device to engage the article at a pickup position andpick up the article from the first conveyor, and means for moving thecarrier to bring the picked up article from the pickup position to adropoff position adjacent the second conveyor whereat the article may betransferred to the second conveyor, the improvement comprising: acontrol disposed to be actuated by the article reaching a preselectedposition spaced from said pickup position; means for causing the pickupdevice to be juxtaposed to the article as an incident of actuation ofsaid control; sensing means for sensing the juxtaposition of the articleto the pickup device at said pickup position; and means responsive tothe sensing of said juxtaposition to initiate raising of the carrier tocause said pickup device to pick up the article and prevent operation ofthe moving means until said article is fully picked up by said pickupdevice.
 2. The article transferring apparatus of claim 1 wherein saidsensing means comprises a proximity switch.
 3. The article transferringapparatus of claim 1 wherein said means responsive to the sensing of thejuxtaposition of the article to the pickup device comprises means forpreventing application of a moving force to the carrier until completionof the raising of the carrier to pick up the article.
 4. The articletransferring apparatus of claim 1 wherein said moving means furthercomprises means for moving the carrier to cause said pickup device topursue said article as it is moving to said pickup position, and saidmeans responsive to the sensing of said juxtaposition comprises meansfor de-energizing the moving means while said carrier is being raised bysaid raising means.
 5. The article transferring apparatus of claim 1wherein said sensing means further comprises means for sensingseparation of the pickup device from the article at the second conveyor,and said apparatus includes further means responsive to a sensedseparation to return the carrier to a start position adjacent the firstconveyor for awaiting the reactuation of said control by a subsequentarticle reaching said preselected position.
 6. In an apparatus fortransferring an article from a first moving conveyor to a secondconveyor, said apparatus having a carrier provided with a pickup device,power means for moving the carrier to cause the pickup device to engagethe article at a pickup position and elevate the pickup device to pickup the article from the first conveyor, and means for moving the carrierto bring the picked up article from the pickup position to a dropoffposition adjacent the second conveyor whereat the article may betransferred to the second conveyor, the improvement comprising: aproximity switch for sensing the engagement of the pickup device withthe article and sensing a transfer of the picked up article from thepickup device to the second conveyor at said dropoff position; meansresponsive to the sensing of said transfer by said proximity switch toinitiate return of the carrier by said power means to adjacent thepickup position; and a control including means for sensing the movementof a subsequent article toward the pickup position and causing operationof said power means to engage the pickup means with said subsequentarticle for picking up said subsequent article from the first conveyor.7. The article transferring apparatus of claim 6 wherein said meansresponsive to the sensing of said transfer comprises means for loweringthe pickup device and, subsequent to the lowering of the pickup device,returning the carrier to adjacent the pickup position, said proximityswitch further including means for sensing when the pickup device haselevated the article to a preselected elevated transfer position.
 8. Thearticle transferring apparatus of claim 6 wherein said means responsiveto the sensing of said transfer comprises means for lowering thecarrier, and means responsive to lowering of the carrier to a retractedlower position for returning the lowered carrier to adjacent the pickupposition.
 9. In an apparatus for transferring an article carried by afirst moving conveyor to a second moving conveyor, said apparatus havinga carrier provided with a pickup device, power means for moving saidcarrier for carrying the pickup device to pick up the article from thefirst conveyor and translate said carrier for transferring the picked uparticle to the second conveyor, the improvement comprising: firstsensing means for sensing juxtaposition of the pickup device to thearticle at a pickup position; means responsive to the sensing of saidjuxtaposition to initiate operation of the power means to cause saidpickup device to pick up the article, said sensing means further sensingwhen said pickup device has fully picked up the article; meansresponsive to said second sensing means sensing that the pickup devicehas not fully picked up said article to preclude translation of saidcarrier by said power means; and means responsive to said second sensingmeans sensing that the pickup device has fully picked up said article toinitiate translation of said carrier from said pickup position totransfer said article to said second conveyor.
 10. The articletransferring apparatus of claim 9 wherein said sensing means furthersenses the removal of the picked up article from the pickup device bysaid second conveyor.
 11. The article transferring apparatus of claim 9wherein said sensing means further comprises means for sensing theremoval of the picked up article from the pickup device by said secondconveyor and means are provided responsive thereto for effecting returnof the pickup device to a starting position for picking up andtransferring a subsequent article from the first conveyor to the secondconveyor.